It has been reported that approximately 99.99% of all natural Uranium on Earth is composed of either 235U or 238U, with 238U comprising 99.28% and 235U comprising 0.71% of all natural Uranium. However, in order to achieve a nuclear chain reaction capable of sustaining a fission reaction in Uranium, a majority of the neutrons released by a fissioning 235U atom must impact other 235U atoms. This requires that the Uranium be enriched such that the percentage of 235U is between 3-5% to sustain a nuclear fission chain reaction, with weapons grade Uranium requiring much higher concentrations of 235U. Typically, such enrichment occurs in gaseous diffusion or centrifuge plants, where Uranium in the form of UF6 is enriched to increase the 235U content. However, when enriching Uranium, it is very important to keep track of the concentration of 235U in the Uranium sample in order to safeguard the plant and its workers, as well as for quality control purposes and to guard against the production of more enriched, potentially weapons grade, Uranium.
Methods of detecting the amount of 235U in a sample are well known in the art: 235U spontaneously radiates 186 keV gamma radiation which can be detected and measured apart from 186 keV background gamma radiation. In order to measure the total Uranium content of a sample, a separate radioactive material source of non-186 keV radiation—typically 109Cd, 241Am or 57Co—is used to irradiate the sample. The count rate of this non-186 keV radiation after being attenuated by a sample container, as well as the count rate of this radiation after being attenuated by the sample container and UF6 in the test sample, allows for the calculation of the enrichment factor of the sample.
Embodiments of the present invention provide for a system in which the energy source is not radioactive and does not decay with time, and where the radiation is emitted from an artificial source preferably utilizing an energetic electron process. It is further desirous that a more accurate enrichment factor is calculable with a lower level of instrument stability and temperature dependence.